[LinuxPPS] LinuxPPS through USB interface

[emorgen at comcast.net]

I read about a year's worth of questions on the forum and I could not find an exact match to my question so I apologise if my question has been answered. 

I have a GPS Eval chip from sparkfun and I wired a connection between the PPS port to the DCD port of the USB connection. Basically this card has two ports, serial and USB. The USB port is a serial converter port. When I try and run ppstest with a pps instance of the usb drive I get the following error: 

time_pps_fetch() error -1 (Connection timed out) 

If I connect the device through a normal serial port I get no issues with PPS. I have tested the connection with a scope and the data is being properly sent along the line. I'm wondering if LinuxPPS does not support USB serial emulation or if there is some setting I need. 

Please let me know if anyone has any tweaks or alternative methods to retrieve when the PPS signal arrives. I don't think LinuxPPS supports other pins so if I send the signal to a different port i'd have to modify the code to read from that port. 

Thank you in advance for any help you provide me. It is greatly appreciated. 

Sincerely, 

Eric Morgenstern 
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